Friable composition and process

ABSTRACT

Friable compositions suitable for use as extrusion aids in polymeric extrusion formulations are prepared by a process which comprises mixing a paraffinic hydrocarbon wax and calcium salt of a fatty acid while heating to a temperature of at least 160°C and thereafter cooling to recover a solid, glass-like, friable composition, said paraffinic hydrocarbon wax having a drop melting point of at least 110°F, an oil content of not greater than 50 percent by weight and a needle penetration value at 77°F in the range of 1 mm to 20 mm, and said fatty acid being a C 16  -C 24  aliphatic hydrocarbon monocarboxylic acid or mixtures thereof.

This is a division of application Ser. No. 465,789, filed May 1, 1974,now U.S. Pat. No. 3,883,363.

This invention relates to a composition derived from paraffinichydrocarbon waxes and calcium salts of certain fatty acids which aresolid, glass-like and friable at ambient conditions. The compositionscan be ground or otherwise reduced to discrete particles having lesstendency to fuse or coalesce than the paraffinic hydrocarbon waxes yetstill begins to become fluidized at elevated temperatures of the orderof 100°C or higher.

Polyvinyl chloride and other thermoplastic extrustion formulationscommonly include paraffinic hydrocarbon waxes and calcium salts ofcertain fatty acids such as calcium stearate as extrusion aids. Sincethe extrusion formulations are generally fed to an extruder as a mixtureof particulate solids, it is desirable that any additives to theformulations, including the abovementioned extrusion aids, be in adiscrete solid, particulate form and capable of being handled as solids.While the calcium salts present no difficulties along this line onlycertain high quality paraffinic hydrocarbon waxes can be used.Relatively soft waxes or those of a less pure nature containingquantities of oils or other solvents are generally unacceptable from amaterials handling viewpoint; e.g., they may not form discreteparticulate solids or they may not sufficiently retain such physicalform on storage or both. As a result, a great many paraffinichydrocarbon waxes are excluded from use with thermoplastic formulationsalthough if it were not for their lack of materials handling capabilitythey would be suitable extrusion aids in such formulations.

In accordance with this invention, there is provided a compositionembodying both paraffinic hydrocarbon waxes and calcium salts which issolid, glass-like and friable at ambient temperatures and can be groundor otherwise reduced to discrete particulate form having less tendencyto fuse or coalesce on standing than the paraffinic hydrocarbon waxes bythemselves. At elevated temperatures; e.g., 100°C, these compositionsbegin to become fluidized. This invention, therefore, provides atechnique for rendering relatively soft, amorphous waxes, or those of aless pure nature, suitable for solids handling situations such as withthermoplastic extrusion formulations. Further, when used inthermoplastic extrusion formulations, there is an added benefit in thata single material provides both the paraffinic hydrocarbon waxrequirement as well as the calcium salt requirement. Quite obviously,the invention is applicable to higher quality harder waxes as well butin such cases the latter advantage mentioned above is mainly realized.

It is emphasized at the outset that the composition of this invention isnot a mere physical blend wherein each component contributes itindividual properties without any interaction with each other. Rather,the physical form of the composition is unlike either of the individualcomponents. The composition is best characterized as being a glass-like,friable solid and might be described as resulting from a synergisticaction between the components. From a physical chemistry standpoint, itis not known what actually occurs in forming the composition althoughsome of those skilled in the art might make analogy to the grease art.

As mentioned previously, the composition of the invention is derivedfrom paraffinic hydrocarbon waxes and calcium salts of certain fattyacids.

The calcium salts which may be employed are those derived from C₁₆ -C₂₄aliphatic hydrocarbon monocarboxylic acids or mixtures thereof. Theseacids may be saturated or unsaturated. When mixtures of the acids areused, they may contain up to about 15 weight percent of a C₁₄ aliphatichydrocarbon monocarboxylic acid of the same saturation characteristicsoutlined above. Illustrative of suitable acids are palmitic, stearic,oleic, linoleic, eicosanic, behenic, tall oil fatty acid, hydrogenatedvegetable fatty acid, hydrogenated tallow fatty acid, distilledcottonseed fatty acid, and the like. Various commercial grades ofsuitable acids are available, some of which are listed in Fatty Acidsand Their Industrial Applications by E. S. Pattison, 1968, at page 7,Table 1-2 (excluding high lauric). These suitable commercial acids aregenerally mixtures of the acids hereinbefore described and mayadditionally have small amounts of certain impurities depending on theirmethod of manufacture.

The suitable paraffinic hydrocarbon waxes are generally derived frompetroleum sources. These waxes contain a variety of hydrocarbonstructures, for example, normal paraffins, iso-paraffins,cyclo-paraffins, small quantities of polycyclo-paraffins and aromaticsand other hydrocarbons and may be in a purified form or may contain oilsdepending upon their source and/or manner of recovery. The paraffinichydrocarbon waxes which are particularly useful are those having a dropmelting point (ASTM D127-63) of at least 110°F, preferably at least145°F, an oil content (ASTM D721-65T) of not greater than 50 weightpercent, preferably not greater than 20 weight percent, and a needlepenetration value at 77°F (ASTM D1321-65) in the range of 1 mm to 20 mm,preferably 1 mm to 10 mm.

The composition of the invention may be prepared by charging the calciumsalt and paraffinic hydrocarbon wax to a heated vessel equipped with anagitator. It may be desirable to melt the wax before charging to thevessel. Small amounts of water may be present as is known in the greaseart. With continued agitation, the ingredients are heated to at least150°C, preferably at least 180°C. During this heat-up time, the waxinitially becomes molten forming a continuous phase in which the calciumsalt particles are dispersed followed by a subsequent increase inviscosity until the mass reaches a homogenous paste-like consistency. Asthe temperature continues to rise, the paste-like mass breaks into aseparate low-viscosity oil-like phase and a heavier paste-like phase.Then the heavier paste-like appears to form soft bead-like masses andthe low-viscosity oil-like phase disappears into the masses. With thetemperature continuing to rise the soft bead-like masses fuse andcoalesce into a homogeneous taffy-like material. It is at this pointthat the final temperature as hereinbefore noted will be reached and thecomposition of the invention is formed. Heating may be continued for ashort period of time to insure completion of the transformation, even tohigher temperatures short of degradative temperatures.

The hot mass is then removed from the vessel and cooled to ambientconditions whereupon the composition becomes a solid, glass-like friablematerial which can be ground or otherwise reduced to a particular formwhich substantially retains its discreteness and integrity. While thecomposition is a solid at ambient conditions and can be easily fracturedor chopped at these conditions, it is perhaps more convenient andsomewhat easier to grind the composition under cryogenic conditions. Ineither situation, the resultant particulate composition at ambientconditions can be easily handled with conventional solids handlingequipment. Further, the particulate composition substantially maintainsits integrity upon standing or being stored.

Generally, the compositions of this invention will be derived from atleast 30 weight percent calcium salt. Amounts of the calcium saltgreater than this may be used as desired depending on the use of theultimate composition. A particularly suitable use for the compositionsof the invention is as extrusion aids in thermoplastic extrusionformulations such as those based on polyvinyl chloride and for thisend-use satisfactory weight ratios of calcium salt to wax may range fromabout 30/70 to about 70/30.

It is also possible to incorporate other additives into the compositionssuch as when they are employed as extrusion aids or lubricants. In theseinstances other processing aids such as polyethylene waxes or acrylatepolymers may be included, pigments such as TiO₂, fillers, and evenreinforcing materials may be included.

The invention will be further illustrated by the following examples.

EXAMPLE 1

A three-necked flask equipped with a mechanical stirrer was charged withabout 100 g of molten paraffinic hydrocarbon wax. The petroleum derivedparaffinic hydrocarbon wax had an average drop melting point of about148°F, an average oil content of about 16 percent, and an average needlepenetration value (77°F) of about 8.1 mm. With continuous stirring about63 g of commercial grade calcium stearate (Witco G 339/S) was addedincrementally while the mixture was heated with a heat lamp totemperatures in the range of 180°-190°C. The mechanical stirrer, it wasnoted, did not provide optimum agitation. In any event, at the180°-190°C temperatures, the mixture was a taffy-like material which,upon cooling to ambient temperatures, became considerably harder andmore friable than the original wax. Due to the less than optimumagitation, some unchanged pockets of wax were present in the finalproduct but, nevertheless, the composition of the invention wasdemonstrated.

EXAMPLE 2

The procedure of Example 1 was again carried out except that 100 g ofthe commercial grade calcium stearate was incrementally added to the waxand an oil bath was used for heating. The final product, on cooling toambient temperatures, was substantially similar to that of Example 1.

EXAMPLE 3

In a comparative experiment, 100 g of molten petroleum derivedparaffinic wax (as used in Example 1) was charged to a Waring blenderand 81 g of commercial grade calcium stearate were added incrementallywith agitation and while heating with a heat lamp to temperatures ofonly about 100°C. After mixing thoroughly at this temperature themixture was cooled to ambient conditions. The final product was verydissimilar to those of Examples 1 and 2 and resembled merely a physicalmixture of the two components; e.g., a powdered solid dispersed througha soft wax. The product was by no means hard or friable.

EXAMPLE 4

Using a Hobart mixer for better agitation, equipped with an electricheating mantel, 255 g of a molten petroleum derived paraffinic wax werecharged followed by incremental addition of 300 g of commercial gradecalcium stearate with agitation and heating. The wax had an average dropmelting point of about 148°F., an average oil content of about 16percent and an average needle penetration value (77°F) of about 8.1 mm.While heating the mixture to about 190°C, it was observed that theseveral phases described hereinbefore in the specification occurred andthe product at the elevated temperatures was homogenous and taffy-like.After cooling to room temperature, it became a hard, friable solid thatcould be ground or chopped easily.

EXAMPLE 5

Using a Brabender with a Sigma blade, about 170 g of a molten (Code 784)were charged followed by incremental addition of about 200 g of calciumstearate (commercial grade - Witco G339/S) with mixing and heating. Thewax had an average drop melting point of about 165°F, an average oilcontent of about 3 weight percent and an average needle penetrationvaluve (77°F) of 1.5 mm. While heating the mixture to about 190°C, theseveral phases described hereinbefore in the specification wereobserved. The product at the elevated temperatures was homogenous andtaffy-like. Upon cooling to ambient conditions, the product became hard,friable and glass-like. The product was then ground into discreteparticles at ambient conditions using a Revel food grinder.

EXAMPLE 6

To demonstrate the unique ability of the compositions of the inventionin retaining their discreteness compared to a commercial wax used as anextrusion aid in PVC formulations, several tests were run as follows:

20 g of a powdered sample (all of which passes a USS 30 mesh sieve) wereplaced in a 100 ml graduated cylinder (2.5 cm diameter). The loosevolume was noted and a weight was placed on top and the initialcompacted volume was noted. The sample was allowed to stand under weightfor 1 hour at room temperature and the volume was again noted. Thesample was the placed in an oven maintained at 60°C for 1 hour and thevolume was again noted.

The particulars of each run together with the results are indicated inthe table.

                  TABLE I                                                         ______________________________________                                                  VOLUME MEASUREMENTS (ml)                                                                            Room                                                                          Temper-                                       Run    Weight            Ini-   ature  60°C                            No.    (g)      Loose    tial   1 Hr   1 Hr                                   ______________________________________                                        1.sup.a                                                                              250      53       45     42      33.sup.d                              2.sup.b                                                                              250      50       46     45     43                                     3.sup.b                                                                              450      57       47     46     44                                     4.sup.c                                                                              450      53       48     46     43                                     ______________________________________                                         .sup.a Commercial paraffinic wax used in thermoplastic formulations as        extrusion aid, Aristowax XL-165.                                              .sup.b Composition of invention prepared as described in Example 4 except     weight ratio of wax to calcium stearate was 0.85/1.                           .sup.c Composition of invention prepared as described in Example 4 except     weight ratio of wax to calcium stearate was 1.1/0.8.                          .sup.d Sample has fused to a solid cake.                                 

EXAMPLE 7

Compositions of the invention may be prepared with similar results usingthe procedure of Example 5 employing calcium palmitate or calciumtallate in place of the calcium stearate.

As indicated hereinbefore, the compositions of this invention aresuitable for use as extrusion aids in polymer formulations intended forprocessing by extrusion. These compositions not only provide therequirements of both the heretofore separately employed waxes and fattyacids salts but they also do not suffer from dusting problems when dryblended into extrusion formulations.

Thus having described the invention in detail, it will be understood bythose skilled in the art that certain modifications and variations maybe made without departing from the spirit and scope of the invention asdescribed herein and defined in the appended claims.

We claim:
 1. In an improved process for the extrusion processing of athermo plastic polymer formulation using extrusion aids the improvementcomprising utilizing an extrusion aid prepared by mixing a paraffinichydrocarbon wax and calcium salt of a fatty acid while heating to atemperature of at least 150°C and thereafter cooling to recover a solid,glass-like, friable composition, said paraffinic hydrocarbon wax havinga drop melting point of at least 110°F, an oil content of not greaterthan 50 percent by weight and a needle penetration value at 77°F in therange of 1 mm to 20 mm, and said fatty acid being a C₁₆ -C₂₄ aliphatichydrocarbon monocarboxylic acid or mixtures thereof.
 2. The invention ofclaim 1 wherein the composition contains additional processing aids. 3.The invention of claim 1 wherein at least 30 weight percent calcium saltis employed in preparing the composition
 4. The invention of claim 1wherein the composition is prepared using a paraffinic hydrocarbon waxhaving a drop melting point of at least 145°F, an oil content of notgreater than 20 weight percent, and an needle penetration value at 77°Fin the range of 1 mm to 10 mm.
 5. The invention of claim 1 wherein thecomposition is prepared using a fatty acid selected from the groupconsisting of palmitic acid, stearic acid, oleic acid, linoleic acid,eicosanic acid, behenic acid, tall oil fatty acid, or mixtures thereof.